The Rhododendron Plant Genome Database (RPGD): a comprehensive online omics database for Rhododendron.

BACKGROUND: The genus Rhododendron L. has been widely cultivated for hundreds of years around the world. Members of this genus are known for great ornamental and medicinal value. Owing to advances in sequencing technology, genomes and transcriptomes of members of the Rhododendron genus have been sequenced and published by various laboratories. With increasing amounts of omics data available, a centralized platform is necessary for effective storage, analysis, and integration of these large-scale datasets to ensure consistency, independence, and maintainability. RESULTS: Here, we report our development of the Rhododendron Plant Genome Database (RPGD; http://bioinfor.kib.ac.cn/RPGD/ ), which represents the first comprehensive database of Rhododendron genomics information. It includes large amounts of omics data, including genome sequence assemblies for R. delavayi, R. williamsianum, and R. simsii, gene expression profiles derived from public RNA-Seq data, functional annotations, gene families, transcription factor identification, gene homology, simple sequence repeats, and chloroplast genome. Additionally, many useful tools, including BLAST, JBrowse, Orthologous Groups, Genome Synteny Browser, Flanking Sequence Finder, Expression Heatmap, and Batch Download were integrated into the platform. CONCLUSIONS: RPGD is designed to be a comprehensive and helpful platform for all Rhododendron researchers. Believe that RPGD will be an indispensable hub for Rhododendron studies.

Temporal regulation of alternative splicing events in rice memory under drought stress.

Plant adaptation to drought stress is essential for plant survival and crop yield. Recently, harnessing drought memory, which is induced by repeated stress and recovery cycles, was suggested as a means to improve drought resistance at the transcriptional level. However, the genetic mechanism underlying drought memory is unclear. Here, we carried out a quantitative analysis of alternative splicing (AS) events in rice memory under drought stress, generating 12 transcriptome datasets. Notably, we identified exon skipping (ES) as the predominant AS type (>80%) in differential alternative splicing (DAS) in response to drought stress. Applying our analysis pipeline to investigate DAS events following drought stress in six other plant species revealed variable ES frequencies ranging from 9.94% to 60.70% depending on the species, suggesting that the relative frequency of DAS types in plants is likely to be species-specific. The dinucleotide sequence at AS splice sites in rice following drought stress was preferentially GC-AG and AT-AC. Since U12-type splicing uses the AT-AC site, this suggests that drought stress may increase U12-type splicing, and thus increase ES frequency. We hypothesize that multiple isoforms derived from exon skipping may be induced by drought stress in rice. We also identified 20 transcription factors and three highly connected hub genes with potential roles in drought memory that may be good targets for plant breeding.

Phylogenetic Analysis of Wild Species and the Maternal Origin of Cultivars in the Genus Lilium Using 114 Plastid Genomes.

Lilies are one of the most important ornamental flowers worldwide with approximately 100 wild species and numerous cultivars, but the phylogenetic relationships among wild species and their contributions to these cultivars are poorly resolved. We collected the major Lilium species and cultivars and assembled their plastome sequences. Our phylogenetic reconstruction using 114 plastid genomes, including 70 wild species representing all sections and 42 cultivars representing six hybrid divisions and two outgroups, uncovered well-supported genetic relationships within Lilium. The wild species were separated into two distinct groups (groups A and B) associated with geographical distribution, which further diversified into eight different clades that were phylogenetically well supported. Additional support was provided by the distributions of indels and single-nucleotide variants, which were consistent with the topology. The species of sections Archelirion, Sinomartagon III, and Leucolirion 6a and 6b were the maternal donors for Oriental hybrids, Asiatic hybrids, Trumpet hybrids, and Longiflorum hybrids, respectively. The maternal donors of the OT hybrids originated from the two sections Archelirion and Leucolirion 6a, and LA hybrids were derived from the two sections Leucolirion 6b and Sinomartagon. Our study provides an important basis for clarifying the infrageneric classification and the maternal origin of cultivars in Lilium.

Rapid Genome Evolution and Adaptation of Thlaspi arvense Mediated by Recurrent RNA-Based and Tandem Gene Duplications.

Retrotransposons are the most abundant group of transposable elements (TEs) in plants, providing an extraordinarily versatile source of genetic variation. Thlaspi arvense, a close relative of the model plant Arabidopsis thaliana with worldwide distribution, thrives from sea level to above 4,000 m elevation in the Qinghai-Tibet Plateau (QTP), China. Its strong adaptability renders it an ideal model system for studying plant adaptation in extreme environments. However, how the retrotransposons affect the T. arvense genome evolution and adaptation is largely unknown. We report a high-quality chromosome-scale genome assembly of T. arvense with a scaffold N50 of 59.10 Mb. Long terminal repeat retrotransposons (LTR-RTs) account for 56.94% of the genome assembly, and the Gypsy superfamily is the most abundant TEs. The amplification of LTR-RTs in the last six million years primarily contributed to the genome size expansion in T. arvense. We identified 351 retrogenes and 303 genes flanked by LTRs, respectively. A comparative analysis showed that orthogroups containing those retrogenes and genes flanked by LTRs have a higher percentage of significantly expanded orthogroups (SEOs), and these SEOs possess more recent tandem duplicated genes. All present results indicate that RNA-based gene duplication (retroduplication) accelerated the subsequent tandem duplication of homologous genes resulting in family expansions, and these expanded gene families were implicated in plant growth, development, and stress responses, which were one of the pivotal factors for T. arvense's adaptation to the harsh environment in the QTP regions. In conclusion, the high-quality assembly of the T. arvense genome provides insights into the retroduplication mediated mechanism of plant adaptation to extreme environments.